Two
Phase Research Projects --- page 1
High Density Heat Flux Cooling Cryogenic
Cooling LHP Transient Modeling Code
Explanation of ALHP Concept (pdf
file)
High Density Heat Flux
Cooling
Unique internal design produces a thin high speed liquid
film that maximizes the heat transfer coefficient. This design does not have
the puddling issues and critical heat flux limitations of traditional spray
coolers or the small effective cooling area restrictions of traditional jet
impingement designs. Initial prototype demonstrated ~9000 W in 2cm a diameter
surface. NASA SBIR project using a dual evaporator design removed over 1 kW
from each 4 cm2 surface, demonstrating the ability to keep the surfaces at or
below 50 C with a heat flux > 250 W/cm2. More details
Cryogenic Loop Heat Pipes
Our research work shows how to transfer cryogenic cooling over a long distance, moving joints, or how to cool a large area such as a large optical surface down to cryogenic temperatures using a single Loop Heat Pipe. Transport distances, working fluids and heat transfer requirements determine the sizes needed for the loop heat design so sizes can vary radically per the design requirements. We have built and tested loops using Nitrogen, Hydrogen, Neon and Helium.
Hydrogen LHP
World’s
first Cryogenic Hydrogen Loop Heat Pipe. Successfully transported 0.25W - 5W
over a distance of 2.5 meters, Evaporator temperature ran between 20 K &
30K, depending on if operating in warm environment (200 K) or a Nitrogen cooled
Shroud. Design also uses a TTH Research innovation referred to as a swing
volume which drastically reduced the hot pressure reduction reservoir volume
size from 1000 cc down to 200 cc. Loop heat pipe design incorporates features
that enables rapid start-ups and a system that can handle parasitic heat gains
on the transport lines. More details
Nitrogen LHP across Gimbaled Joint
Cryogenic Loop Heat Pipe that
uses Nitrogen as its working fluid and transfers 5 to 10 W across a gimbaled
joint that has an azimuth rotation of +/- 200 degrees and elevation rotation of
90 degrees. Prototype loop
transferred 20 W over 2.5m distance, using Nitrogen as the working fluid. More
details
Large Area Cooling
This concept demonstrates how to
use a single capillary pump to cool a large surface area. Unlike a regular loop heat pipe,
in this application the capillary pump is utilized not to acquire heat from
the heat source but simply to generate a fluid mass flow in the loop and
use that flow to cool down a large area. Prototype tests used Neon to remove 4.2W from a 48 in2
area. A program using this concept
with Helium is currently in progress.
More details
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Two
Phase Transient Modeling Code
This code was developed
under SBIR funding at NASA/Goddard to allow thermal analysts who are familiar
with SINDA or other thermal analytical codes to be able to model Loop Heat
Pipes without being an expert on Loop Heat Pipe operations and fluid
mechanics. The user will simply
define the external connections to the Loop Heat Pipe, such as defining the
conduction of the radiator plate to the outside of the Loop Heat Pipe condenser
lines and the loop heat pipe code will take care of the Loop Heat Pipe thermal
model definitions and work with the SINDA (or other thermal programs) heat
transfer calculations to provide the Loop Heat Pipe predictions. The user has the option to specify their
own loop heat pipe dimensions or use defaults provided by the code.